People often ask how rammed earth walls are actually constructed. This article will detail the setup, mixing, compaction, and strip-down processes of constructing a rammed earth wall.
𝐑𝐚𝐦𝐦𝐞𝐝 𝐄𝐚𝐫𝐭𝐡 𝐅𝐨𝐫𝐦𝐰𝐨𝐫𝐤
We use specialized rammed earth formwork constructed from steel and covered with a structural plyboard which creates an ‘Off Form Finish’.
Off-form finishes mean the final finish of the wall is what you see when the formwork is removed, a textured finish that is then sealed.
The formwork ranges in length from 600mm to 2400mm and in vertical heights of 300mm and 600mm.
The design of the formwork allows them to be joined together to increase the length of the wall where required, depending on the plan.
It is important to understand that the type of soil used to construct your rammed earth walls will determine the length that can be built in each setup but generally should not exceed 4500mm in length.
𝐒𝐞𝐭𝐭𝐢𝐧𝐠 𝐮𝐩 𝐑𝐚𝐦𝐦𝐞𝐝 𝐄𝐚𝐫𝐭𝐡 𝐅𝐨𝐫𝐦𝐰𝐨𝐫𝐤
The first step in constructing rammed earth walls is marking exactly where the walls will be built on the concrete slab or footings.
At this stage, consideration must be given to the overall aesthetics of the build and floor plan, as articulation joints are required in all masonry walls.
Articulation joints are vertical joins between wall panels that help to control linear shrinkage of the material – to prevent cracking in the wall as it cures (dries) and to allow for concrete slab and footing movement without cracking the wall.
The first formwork lift is set up by placing a formwork panel on either side of the marked-out area where the wall is to be built, inserting spacers to separate the two formwork panels at the required wall thickness, these are then bolted together.
End shutters are inserted at either end of the formwork panels to form the ends of the wall being built.
The final stage in setting up is to level the end shutters so that the wall will be vertical (900) when built. The above process is repeated for each section of the wall being built.
𝐑𝐚𝐦𝐦𝐞𝐝 𝐄𝐚𝐫𝐭𝐡 𝐂𝐨𝐧𝐬𝐭𝐫𝐮𝐜𝐭𝐢𝐨𝐧
An earth/cement mixture is then combined with water to create the correct moisture level for rammed earth wall construction.
A quick guide to calculating whether the mixture is at the right moisture level is to squeeze it in your hand – if it holds together after this, then crumbles when dropped, it is ready to be compacted.
Once the moisture level is right, the earth mixture is hand shoveled into the formwork in 150mm deep increments and compacted down with pneumatic tampers.
This process is repeated until the compacted earth is at the top of the formwork lift. The formwork setup process is then repeated along with the compacting for every consecutive lift until the wall reaches its completed height.
To construct rammed earth over doors or windows, we utilize engineered T-Bar lintels, which are placed over the opening during ramming to support the earth above the opening.
When recesses are required in walls, formers are placed into the formwork set up and soil is placed and compacted around them to produce the required opening or shape in the wall.
In the top 600mm of the wall, metal rods are inserted during compacting to provide a tie-down system for a timber top plate, this is for securing the roofing structure.
Electrical conduits and wall boxes are rammed into the wall at points where power points and light switches are required.
Conduits are also placed into the wall to allow water plumbing pipes to be inserted where required.
Where an area is to be tiled over or hidden by joinery, plumbing pipes can be chased (cut) into the wall. The completed wall is left in form overnight whilst initial curing takes place.
𝐑𝐞𝐦𝐨𝐯𝐚𝐥 𝐨𝐟 𝐅𝐨𝐫𝐦𝐰𝐨𝐫𝐤
The formwork is then removed ‘stripped-down’ the following day and any formers placed in the wall during construction are removed.
The newly stripped wall is then detailed to repair minor imperfections, removing any earth that has protruded through bolt holes in the formwork, as well as plugging holes where bolts were inserted through formwork.
As mentioned above, the wall surface is an Off Form Finish, exhibiting the natural beauty and character that is unique to a rammed earth wall.
𝐑𝐚𝐦𝐦𝐞𝐝 𝐞𝐚𝐫𝐭𝐡 𝐢𝐬 𝐚𝐥𝐥 𝐚𝐛𝐨𝐮𝐭 𝐞𝐧𝐝𝐮𝐫𝐚𝐧𝐜𝐞.
There’s a timelessness about a house built with raw earth. Not surprising though since building with earth is truly prehistoric.
Yet rammed earth is very contemporary. In fact, still today, over half of Earth’s population dwells in earthen housing.
The process of creating walls is done by ramming or compacting, earth into forms that create straight sturdy walls. Various types of earth can be used to create striations in distinctive hues mimicking natural earth formations.
Rammed earth techniques create beautiful thick walls that won’t contract and expand but surface cracks may occur, adding additional character without any compromise to the structure.
𝐁𝐞𝐧𝐞𝐟𝐢𝐭𝐬 𝐨𝐟 𝐫𝐚𝐦𝐦𝐞𝐝 𝐞𝐚𝐫𝐭𝐡 𝐚𝐫𝐞:
°It’s regional (making it easily attainable), natural, durable, strong, provides excellent thermal mass, load-bearing, natural, and of course, recyclable.
°Fireproof and characteristically substantial, giving them the ability to withstand strong winds, floods, and hurricanes far better than a traditional stick-framed home.
°Relatively low-cost-after all raw earth is abundant and practically free.
°Well suited for solar heating and cooling.
°Beauty, practicality, quiet, and a distinguished sense of place.
In case you want to try it
In case you want to experience rammed earth construction, Urban Concrete Contractors have done this before and can be reached at 0788901008.